GFAP is an intermediate filament of astrocytes in the central nervous system that is markedly up-regulated following toxic injuries to the brain. Quantitation of GFAP levels has been proposed as a useful screening tool for neurotoxicity testing. We have developed a novel strain of transgenic mice expressing the green fluorescent protein (GFP) in astrocytes under the control of the GFAP promoter. Funding is requested to support pilot studies on these mice, utilizing known neural toxins, to demonstrate the utility of monitoring transgene expression rather than GFAP itself for neurotoxicology screening. Our specific aims are to l) determine optimal conditions for quantitating transgene expression in fixed specimens or tissue extracts, 2) test toxins with well-established activity in the central nervous system (MPTP and kainate) for comparison between the traditional and proposed methods for quantitating the glial response, and 3) investigate whether transgene expression in the retina can serve as a model of CNS response to toxins. Our goals are to develop a standardized protocol for quantifying transgene expression and demonstrate the advantages of this new technology for toxicity screening. PROPOSED COMMERCIAL APPLICATIONS: Federal law requires extensive testing of new chemicals and pharmaceuticals for potential toxicity prior to release as commercial products. The GFP transgenic assay would provide a rapid alternative to a current key test in neurotoxicity evaluation, thus offering substantial savings in labor.